This invention relates in general to roof coverings, and in particular to roof coverings such as asphalt-based roofing shingles that are conventionally protected with a top layer of roofing granules.
Current asphalt-based roofing shingles include an upper surface of roofing granules that helps to protect the shingles from weathering. A recent development is the use of roofing granules coated with reflective pigments that reflect solar radiation. Known as “cool granules”, these roofing granules help to reduce the costs of cooling buildings such as homes that are covered by the roofing shingles. One disadvantage of using roofing shingles with cool granules is that the rough granulated surface provides opportunities for the light to be absorbed, so that it is only possible to achieve a solar reflectivity of about 25% with these granules. Another disadvantage is that these granules are pastel colored, and customers often prefer darker colored shingles. A further disadvantage of cool granules is their high cost, currently about five times the cost of conventional roofing granules.
It is known to make roof coverings without roofing granules. For example, U.S. Patent Application Publication No. 2005/0210808 discloses a roofing membrane including a roofing mat coated with a thermoset or thermoplastic polymer or a polymer-modified bitumen, and is preferably selected from polyvinyl chloride and other resinous compositions containing polyvinyl chloride, CSPE, CPE, EPDM, APP modified bitumen, SBS modified bitumen, and thermoplastic olefins such as polypropylene. The membrane includes a design printed with ink on its top surface, such as an image of laid roofing. The top surface of the membrane may also be textured, for example, to simulate granules. The membrane may be sealed with one or more coatings to provide additional protection from the sun, weather or other elements.
U.S. Patent Application Publication No. 2004/0014385 discloses a roofing shingle including an asphalt-coated roofing mat, an aesthetic web on top of the coated mat, and no roofing granules. The aesthetic web may comprise a metal film or a film to simulate granules, or any other such material to provide an aesthetic top surface.
There is still a need for improved roof coverings that are made without roofing granules.